如何从数据库创建JSON树

import json
import pymysql

# 连接数据库
conn = pymysql.connect(host='localhost', user='username', password='password', db='database')
cursor = conn.cursor()

# 查询数据库数据
sql = "SELECT id, parent_id, data FROM tree_table"
cursor.execute(sql)
results = cursor.fetchall()

# 构建节点对象
nodes = {}
for row in results:
    node_id = row[0]
    parent_id = row[1]
    data = row[2]
    nodes[node_id] = {'id': node_id, 'data': data, 'children': []}

# 构建树结构
root = None
for node_id, node in nodes.items():
    parent_id = node['parent_id']
    if parent_id in nodes:
        parent_node = nodes[parent_id]
        parent_node['children'].append(node)
    else:
        root = node

# 转换为JSON格式
json_tree = json.dumps(root)

# 关闭数据库连接
cursor.close()
conn.close()

print(json_tree)